This invention relates to an apparatus for applying liquid to a roller, and more particularly, to an apparatus for applying liquid to the contacting surface of a roller used in pressing an elongate string to a moving workpiece.
In the plywood industry, successive veneer pieces such as those that are used in making core pieces in the plywood, are commonly held together with a string which is impregnated with a hot-melt adhesive. The impregnated string is heated and then pressed against the face of a veneer piece by a roller mounted on a frame.
In the above-described operation, a thin film of liquid, which is usually water, must be applied to the roller surface in order to effect release of the string from the roller. Typically, an elongate sponge or felt strip extending across the contacting surface of the roller is used to apply the water. Unfortunately, however, so applied the water tends to drip from the pad onto the veneer as the roller presses against the string, causing excess water to be deposited on the veneer. Problems are subsequently incurred when the veneer piece with such excess water is incorporated into plywood, such as "blow-outs" occurring.
A further problem associated with this process is caused by the accumulation of lint, dirt and wood fiber debris on the sponge or felt strip, which often results in the formation of a debris barrier preventing water transfer. When this occurs, the strip must either be cleaned with a pressurized air stream or replaced, thus necessitating work stoppage.
A general object of this invention is to provide an apparatus for applying a thin film of liquid to the contacting surface of a roller used in pressing a string to a workpiece in a manner which inhibits unrestricted flow of liquid onto the roller and the workpiece.
Another object is to provide an apparatus for scraping lint, dirt and wood fiber debris from the contacting surface of the roller.
A further object is to provide such an apparatus which may be quickly removed or replaced for performance of routine maintenance operations with a minimal interruption of production.
A preferred embodiment of the proposed invention includes a plate or shoe, usually made of brass, which has a curved face that conforms to the curvature of the contacting surface of a roller and a liquid-holding well indented inwardly in and surrounded by the curved face. The shoe face terminates in a sharpened edge which is used for scraping debris from the surface of the roller. A tube connected to a water reservoir supplies the well in the shoe with water. Further, the well is closed off by a water permeable pad, such as felt, which acts to inhibit unrestricted flow of water from the well onto the roller. A spring with a manually releasable detent, which seats on a groove in the shoe, urges the curved face of the shoe toward the contacting surface of the roller thereby effecting sealed contact therewith.
With the construction described, it can be seen that this apparatus applies a thin film of liquid to the roller surface in a manner which inhibits unrestricted flow of liquid onto the roller. Further, problems caused by debris buildup, which could eventually halt production, are reduced or eliminated due to removal of debris by the sharpened edge of the shoe. It is also apparent that the shoe may be easily and quickly removed by manual release of the spring detent.
Although this description has referred specifically to the plywood industry, it will be appreciated that it can be used in other applications as well, such as in the fabric industry where adhesive is used to join fabrics.